This invention relates to a two cycle internal combustion engine and more particularly to an improved fuel injection system for such an engine.
It has been recognized, almost since the inception of the internal combustion engine, that there are certain advantages in injecting fuel directly into the combustion chambers either alone or along with high pressure air. Such injection systems tend to improve the distribution of the fuel within the combustion chamber and also can provide better control, under some instances, of the fuel/air ratio within the combustion chamber and the residual charge. The latter advantage is particularly useful in conjunction with two cycle internal combustion engines wherein there must be large degrees of overlap between the opening of the scavenge ports and the closing of the exhaust ports. By employing a fuel injection system directly into the combustion chamber, it can be insured that there will be good scavenging while insuring against the loss of unburned fuel into the exhaust system. However, there are some disadvantages to the use of direct fuel injection, particularly in two cycle internal combustion engines
Because of the fact that the engine has a firing impulse for each revolution of the crankshaft, the heat loading on certain components such as the pistons are higher than with four cycle engines. When all of the fuel is introduced directly into the combustion chamber, there is no cooling of the piston by the admission of fuel and air into the crankcase chamber and then transfer into the combustion chamber, as is typical with two cycle engines wherein the fuel/air charge is introduced into the crankcase chamber. The discharge of fuel into the crankcase chamber tends to cool the pistons because of the evaporation of the fuel and other factors.
In addition, it is difficult to provide adequate fuel/air ratio control with a fuel/air injection system under all running and load conditions. That is, if the injection system is designed so as to provide all of the necessary fuel for high speed running, the engine will tend to run rich at low speeds since it is difficult to accurately maintain the amount of fuel discharge at low speeds through a single air/fuel injection nozzle.
It is, therefore, a principal object of this invention to provide an improved fuel injection system for an engine.
It is a further object of this invention to provide an improved fuel/air injection system for a two cycle internal combustion engine operating on the crankcase compression principle.
It is yet another object of this invention to provide an improved fuel injection system for a two cycle engine that embodies direct injection but wherein the piston and other associated components will be cooled under all running conditions.
It is a further object of this invention to provide an improved and simplified air/fuel injection system that will provide accurate and proper air/fuel ratio controls under all running conditions at a relatively low cost.